If you only remember one number from this whole blog, it would be this: wet food contains about 75 to 80% water, dry kibble around 8%. The entire issue of cat hydration lies in this difference.
The simple calculation
A cat needs about 50 to 60 ml of water per kilo per day, from all sources combined. For a 4 kg cat, that's 220 ml.
Fed wet food: a large part of this volume goes directly into their food bowl. They have relatively little left to drink, which is why these cats seem to "never drink." They don't need to.
Fed dry kibble: the food provides almost nothing. Almost all of the required water must come from drinking. However, cats, descended from animals in arid zones, have a poorly developed sense of thirst: they don't spontaneously compensate. This is where the gap silently widens.
Why it's not obvious
A slightly dehydrated cat doesn't look sick. It plays, eats, purrs. This is what makes the subject insidious: nothing alerts you on a daily basis.
Let's be precise and honest here: we are not claiming that kibble makes a cat sick, nor that a fountain prevents anything. What we are saying is simpler and verifiable: a cat fed dry food must drink more, and many cats don't do it spontaneously. Improving their drinking conditions is common sense, not a treatment.
Three ways to increase their water intake
1. Introduce wet food into their diet. This is by far the most powerful lever. Even a partial transition—one portion of wet food per day instead of one portion of kibble—significantly changes the total. Transition gradually, over one to two weeks, to avoid digestive issues and refusal.
2. Improve the water itself. A large, shallow bowl (its whiskers shouldn't touch the sides), made of ceramic or stainless steel rather than plastic, refilled daily, far from the food bowl and very far from the litter box.
3. Put water in motion. Cats instinctively prefer running water to stagnant water. A fountain plays on this reflex rather than against it: you don't force them to drink, you make the water more appealing.
What if I don't want to switch to wet food?
This is a legitimate choice—cost, smell, preservation, cat preferences. In this case, drinking water becomes even more important, and it's worth paying a little attention to it: several water points in the house, refilled daily, and possibly a fountain if your cat already shows a liking for the tap.
For any questions about your cat's diet, especially if they have a medical history, your veterinarian remains the contact person.